The return on investment (ROI) of software process improvement (SPI) methods is the amount of money gained, returned, or earned above the resources that are spent. ROI is a solid measure of how much additional money we have gained, saved, or received from using a SPI method. ROI begins to clear the landscape. It helps us determine whether the SPI method was worth all of the time, trouble, expense, and investment in a new SPI method. Once again, there are only two parts, terms, or components to the simple ROI equation: benefits and costs. We have already identified the benefits of our chosen SPI method and the costs up to this point. Essentially, ROI consists of dividing the benefits by the costs.

However, the ROI model requires an additional manipulation of the benefits and costs. Before dividing the benefits by the costs, the costs must first be subtracted from the benefits. What? The ROI model assumes that the benefits are not truly benefits until the costs have first been eliminated, paid for, or covered. That is, benefits usually represent the gross windfall, savings, or revenue of using a SPI method. However, in order to achieve the benefits, some measure of investment is required. Therefore, the benefits came at a cost that must be accounted for, isolated, and eliminated. That is what the ROI model does. First, we will identify our benefits. Then we will subtract from the gross benefits the costs that were necessary to achieve the benefits. Then we...